Investigation on subgrade reaction of pile with taking effects of cyclic shear strain of soil into account

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To propose guideline of scaling factors for subgrade reaction of pile in liquefied ground, effects of cyclic shear strain of soil on subgrade reaction of pile are investigated. The following conclusions may be made: 1) With increasing the relative displacement between piles and soil, the subgrade reaction increases due to recovery of effective stress. With cyclic shear strain of soil, the recovery of effective stress is insignificant and then the subgrade reaction decreases. The decrease in subgrade reaction due to cyclic shear strain is more significant in loose soil than in dense soil; 2) The scaling factor for subgrade reaction might be defined by cyclic number and amplitude of shear stress. The estimated subgrade reaction is in good agreement with the observed one both before and after liquefaction; 3) A decrease in subgrade reaction induces a decrease in shaft friction of piles. This suggests that it is important to consider the equilibrium of vertical load as well as that of horizontal load.